ABSTRACT
INTRODUCTION Mycotoxins are extrolites produced by filamentous microfungi that can cause disease in vertebrate animals when introduced via a natural route: ingested, absorbed through the skin or inhaled. This definition excludes fungal toxins which are active against bacteria, archaea, algae, protozoa, and non-vertebrate animals such as insects, spiders, worms, snails and jellyfish. It also excludes toxins produced by Basidiomycetes, i.e., mushrooms and related fungi, because these toxins are ingested by eating fruit bodies, a problem different from the ingestion of toxins produced by microfungi. The definition of microfungi is not rigorous, but understood here to refer principally to Ascomycetous fungi, including those with no sexual stage. The subkingdom Zygomycotina apparently contains few mycotoxin producers, including genera such as Rhizopus and Mucor, are not necessarily excluded from potential mycotoxin producers, but compounds of sufficient toxicity to be termed mycotoxins have not been found in these genera, except for rhizonin A and B from Rhizopus microsporus (Jennessen et al., 2005). All fungi produce extrolites, but fortunately only some of these are toxic to vertebrates. Some mycotoxins are acutely toxic, some are chronically toxic and some are both. Furthermore it is possible that mixtures of mycotoxins act synergistically or additively, so a mycological examination of the mycobiota, to species level, is very important, as different
species produce different profiles of extrolites (Frisvad and Samson, 2004a). Prevention of mycotoxin formation should rely on accurately identified fungi and determination of the mycotoxins and other extrolites the fungi produce. Knowledge of the physiology of the different species is important, not only regarding growth lag phase and growth rate, but also regarding conidium production and further extrolite production. Mycotoxins and other extrolites may be produced in large amounts on some media and not on other media, so a detailed knowledge of the influence of the substrate on mycotoxin production is particularly important. Many mycotoxins may be produced under artificial laboratory conditions, but not necessarily on food, feedstuff or other substrates. Extrolites other than mycotoxins may also be a serious problem, a problem usually overlooked. For example penicillin is produced by P. nalgiovense and P. chrysogenum, species often found or deliberately used as starter cultures, in mouldfermented salami products. The contamination of foods with penicillin and other pharmaceutical compounds should also be avoided. Furthermore allergy problems, maybe initiated by living in water damaged buildings, may later be a problem if mouldy foods with the same fungal species are encountered. In the present chapter we will focus on the qualitative relationship between fungal species and their mycotoxin production, in worst case situations.
